1. Field
This patent specification generally relates to power supplies, and more particularly, to power supplies suitable for instruments such as mobile phones and information terminals using batteries as electric power sources.
2. Discussion of Background
Mobile phones, mobile information terminals, and similar devices include power supplies using batteries as electric power sources and convert a voltage into a prescribed level and supply each function block such as a processor of the mobile phone therewith.
Japanese Patent Application Laid Open No. 11-265234 refers to a power supply that attempts to lower power consumption by controlling a power supplying circuit such as a DC/DC converter, a voltage regulator, etc., to be dependently driven.
Such a power supply is illustrated in FIG. 17, and supplies a driven circuit 65 with electric power from a first battery 70 via a power supplying circuit 62 and diode 64. Electric power from a second battery 61 is also supplied to a driven circuit 65 via a diode 63.
The second battery 61 and diode 63 are provided as a backup when other power is blocked.
One or more primary power supplying circuits 71 are connected to battery 70. To the primary power supplying circuits 71, a secondary power supplying circuit 72 is connected. The primary power supplying circuits 71 supply a first driven circuit 81 with electric power, for example of 3.0 v, via a power source line 91. The secondary power supplying circuit 72 supplies a second driven circuit 82 with electric power, for example of 2.0 v, via a power source line 92. The first and second driven circuits 81 and 82 are connected to each other via a data line 83. The second driven circuit 82 receives and processes the data that is output from the first driven circuit 81 via the data line 83. The first driven circuit 81 receives and further processes the data that is output from the second driven circuit 82.
These first and second driven circuits 81 and 82 do not necessarily simultaneously start operations. Specifically, the first driven circuit 81 operates from time to time. The second driven circuit 81 operates only whenever the first driven circuit 81 operates, i.e., never operates alone.
A control circuit 73 is provided and includes a voltage detection circuit 130 and a secondary electric power control section 131. The control circuit 73 is ready to supply a scheduled voltage when the primary electric power supplying circuit 71 starts operating and a prescribed time has elapsed thereafter. A first voltage detection section provided in the voltage detection circuit 130 outputs a High signal to the secondary electric power control section 131 when a supplied voltage to the primary electric power supplying circuit 71 reaches a prescribed level. In addition, a first oscillation section provided in the secondary electric power control section 131 starts oscillation when the primary electric power supplying circuit 71 starts operating. However, the first oscillation section requires a prescribed period of time until the oscillation condition is stabilized.
A primary reset signal generation section provided in the secondary electric power control section 131 includes a pair of flip-flops, and outputs a High reset signal after a prescribed period of time has elapsed when a first voltage detection section of the voltage detection circuit 130 outputs a High signal. The reset signal is given to the first driven circuit 81. The first driven circuit 81 receiving the High reset signal achieves the above-described stable oscillation output at that time, and starts operating with a necessary electric power via an power source line 91 from the primary electric power supplying circuit 71.
After having processed and transferring data to the second driven circuit 82, the first driven circuit 81 gives an instruction signal to the secondary power supply control signal generation section of the secondary electric power control section 131 so as to enable the second driven circuit 82 to operate. When receiving the instruction signal, the secondary power supply control signal generation section gives a secondary electric power supplying control signal to both the secondary power supplying circuit 72 and a second voltage detection section provided in the voltage detection circuit 130. In addition, a detection output of the first voltage detection section is input to the secondary electric power supply control signal generation section. The secondary electric power supply control signal generation section controls the secondary power supplying circuits 72 not to operate even if receiving the above-described instruction signal, until obtaining a High signal as the above-described detection output. The secondary electric power supply control signal generation section controls the secondary power supplying circuit 72 to stop operating when the above-described detection output is a Low signal.
When receiving the secondary electric power supply control signal of a High level, the second voltage detection section starts detecting. In addition, the secondary power supplying circuit 72 starts operating upon receiving the secondary electric power supply control signal. When the secondary power supplying circuit 72 starts operating, a condition capable of supplying a scheduled voltage is established a prescribed period of time thereafter.
The second voltage detection section of the voltage detection circuit 130 outputs a High signal to the secondary electric power control section 131 when a supplied voltage to the secondary power supplying circuit 72 reaches a prescribed level. In addition, a second oscillation section of the secondary electric power control section 131 starts oscillating when the secondary power supplying circuit 72 starts operating, and requires a prescribed period of time until the oscillation condition becomes stable.
The second reset signal generation section of the secondary electric power control section 131 outputs a reset signal of a High level after a prescribed period of time has elapsed from when the second voltage detection section of the voltage detection circuit 130 outputs a High signal. The reset signal is given to the second driven circuit 82. After receiving the reset signal of the High level, the second driven circuit 82 achieves the above-described stable oscillation output from that time, and starts operating with necessary electric power supplied via the power source line 92 from the secondary electric power supplying circuit 72. In addition, the above-described second oscillation section and second reset signal generation section drive with electric power supplied from the secondary electric power supplying circuit 72.
The above-described configuration can lower the power consumption when compared with a configuration in which a dependent electric power supplying circuit (i.e., a secondary electric power supplying circuit) dependently operates when a main electric power supplying circuit (i.e., a primary electric power supplying circuit) operates. Specifically, power to the dependent electric power supplying circuit can be supplied only when needed.
Recently, two or more power sources requiring dependent control are utilized in core (e.g. CPU) and I/O sections in a device (e.g. LSI) of an instrument, such as a mobile phone, a mobile information terminal, etc., including a battery as a power source.
Specifically, in such a conventional system as illustrated in FIG. 18, electrical power of a power source 101 composed of a battery is given to a driven circuit from a power supplying circuit. In addition, a control signal is given to one or more devices 1101 to 110n (i.e., dependent relation devices), in which two or more power sources used in a core section and an I/O section are to be dependently controlled, from a control signal generation circuit 102. Electric power is supplied to the dependent relation devices 1101 to 110n from the power source 101 based upon an electric power supply control signal output from an electric power supply control circuit.
A power supplying circuit 111 is provided in the dependent relation device 1101 and supplies power to a driven circuit 112, in which two or more power sources should be dependently controlled to be supplied to the core section and I/O section (i.e., a voltage input section).
In such a situation, even if a circuit section operable with a low voltage is utilized in the device 1101, the power consumption of device 1101 is not lowered because a single power source needs to match the highest voltage circuit included in the device 1101.
As illustrated in FIG. 19 as one example, each of the dependent relation devices 1101 to 110n includes a plurality of power supplying circuits 1111 to 111n, so as to supply power to the driven circuit 112. In addition, a system controller gives electric power supply control signals for turning ON/OFF a driven circuit, and controls each of the plurality of power supplying circuits 1111 to 111n. 
According to this configuration, since an optimal operation voltage is supplied to the driven circuit in the device, power consumption can be lowered in a system of the type illustrated in FIG. 18. However, respective power supplying circuits 1111 to 111n should be controlled depending upon an operation speed of a system.
A technology discussed in Japanese Patent Application Laid Open No. 11-265234 can be applied to a system having the power supplying circuits 1111 to 111n having dependent relation.
Specifically, the voltage 1 input section of the driven circuit 112 of FIG. 19 which receives electric power from the power supplying circuit 1111, corresponds to the first driven circuit of FIG. 17. Whereas, the voltage 2 to n input sections thereof which receive respective electric power from the power supplying circuits 1112 to 111n corresponds to the second driven circuit.
In such a situation, the second driven circuit of the voltage 2 to n input sections can be independently controlled. Otherwise, respective third to n-th driving circuits can be connected and dependently controlled.
Further, when a device wherein two or more power supplies are to be provided in its core and I/O sections and need to be dependently controlled corresponds to the second driven circuit of Japanese Patent Application Laid Open No. 11-265234, the voltage 1 input section, which receives electric power from the primary power supply of the driven circuit, serves as the second driving circuit. Also, the voltage 2 to n input sections, which receive electric power from the secondary power supplying circuit, serve as a third driving circuit.
In such a situation, the third driving circuit of the voltage 2 to n input sections independently controls. Otherwise, respective 4 to n+1 driving circuits are connected and dependently controlled.
However, when electric power is to be supplied to a device where two or more power supplies are dependently controlled in the core and I/O sections, the voltage 1 input section is necessarily firstly supplied with electric power, and the voltage 2 to n input sections are controlled to selectively receives power supply. As a result, the above-described conventional technology is incapable of performing complex dependent power supply control by an optimal timing for the voltage 2 to n input sections.